In general, in a solid electrolyte fuel cell (SOFC), an electrolyte electrode assembly (MEA) in which an anode electrode and a cathode electrode are disposed on both sides of an electrolyte is sandwiched between separators (bipolar plates). An oxide ion conductor such as stabilizing zirconium oxide is used as this electrolyte. The fuel cell is used as a fuel cell stack in which a predetermined number of electrolyte electrode assemblies and separators are stacked.
In recent years, a flat plate-shaped seal-less type solid electrolyte fuel cell has been developed. Such a seal-less type fuel cell has advantages such as the structure thereof is simplified and the load applied to the electrolyte electrode assembly is decreased, in comparison with a sealed type fuel cell.
Patent Citation 1 discloses a technique of providing flexibility to a connecting portion which connects a manifold portion of the separator and a portion where a power generating cell located. Since, the connecting portion has flexibility to an applied load, the load applied to the separator can be divided into the manifold portion and the portion where the power generating cell located, and thereby the load can be suitably applied to both the portions.
However, in the technique described in Patent Citation 1, since unused reactant gas (fuel gas and oxygen-containing gas) is uselessly discharged from a circumferential portion of the power generating cell, there is a problem that the reactant gas cannot be used efficiently.
Patent Citation 2 discloses a technique of providing a cover having gas outlets so as to cover the outer circumferential portion of a fuel electrode current collector, thus restricting discharge positions of surplus gas discharged from the outer circumferential portion. Accordingly, the useless discharge of gas from the outer circumferential portion of the fuel electrode current collector can be prevented.
However, the technique described in Patent Citation 2 has problems that the number of components and the manufacturing costs increases due to the providing of the cover which is a component separate from the separator. Since the thickness of the fuel cell increases, there is a problem that the fuel cell stack increases in size in the stacking direction.
In addition, Patent Citation 3 discloses a technique of forming a separator by pressing a thin circular plate formed of a nickel-chrome alloy. The separator described in Patent Citation 3 includes a first manifold of fuel gas, a first gas passage of fuel gas, a first orifice groove which is communicated with the first gas passage, and a first power collecting projection on an anode electrode side. In addition, on a cathode electrode side which is disposed on the opposite side of the anode electrode, the separator also includes a second manifold and a second gas passage of oxygen-containing gas opposite to the first power collecting projection, and includes a second power collecting projection opposite to the first manifold and the first gas passage. Additionally, a second orifice groove which is communicated with the second gas passage is provided at the side end portion of the separator.